Converting Legal Description to GPS Waypoints

gc2rangerbob@yahoo.com

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11-26-2005, 04:02 AM

I have a nearly square 20 acre property in North Idaho which has been
surveyed. I know the physical location of one of the metal survey
markers. I want to locate the other 3 corner markers. Is there a way I
can convert the legal decription data into a form that is usable in a
GPS to enable me to at least come close to the marker locations.

Here is part of the legal description so you know what you know the
type of information I have:

"A tract of land in the North half of Section 17, Township 58 North,
Range 1 East, boise Meridian, Bonner County, Idaho more specifically
described as follows:

Beginning at a point on the North line of said Section 17, distant
South 80-05-10 West 4231.19 from the Northeast corner of said Section
17;

thence south 0-30-34 East 822.01 feet, more or less, to a 1/2 inch
rebar as noted on Survey, recorded July 2, 1979 under Instrument No.
XXXX and also noted on Survey recorded October 12, 1986 under
Instrument No. XXXX, records of Bonner County, Idaho;

thence south 89-05-09 West (also known a North 89-57-42) a distance of
1059.49 feet,more or less to the West line of said Section 17;

etc etc....

If a GPS will be useful, please let me know if there is any particular
functionality I will need. Or maybe I could do this just as easy with a
compass.

Those are "Quadrantal Bearings", a Google search will lead to lots of
explanations. The one at ccsu.edu was easy reading.

I didn't have any real starting reference for GPS measurements, but I could
still find the corner posts using the directions and distances.

I was also able to locate a parcel map of my property, overlaid onto
topographic maps and aerial photos, at my county web site. Side by side
comparison of that, with the same maps exposed in ExpertGPS, allowed me to
make waypoints for my GPS that let me use my GPS to find the corner markers
for my property. Try a google search of XXX county gis mapping.

>I have a nearly square 20 acre property in North Idaho which has been
> surveyed. I know the physical location of one of the metal survey
> markers. I want to locate the other 3 corner markers. Is there a way I
> can convert the legal decription data into a form that is usable in a
> GPS to enable me to at least come close to the marker locations.
> Here is part of the legal description so you know what > described as
> follows:
> Beginning at a point on the North line of said Section 17, distant
> South 80-05-10 West 4231.19 from the Northeast corner of said Section
> 17;
> thence south 0-30-34 East 822.01 feet, more or less, to a 1/2 inch
> rebar as noted on Survey, recorded July 2, 1979 under Instrument No.
> XXXX and also noted on Survey recorded October 12, 1986 under
> Instrument No. XXXX, records of Bonner County, Idaho;
> thence south 89-05-09 West (also known a North 89-57-42) a distance of
> 1059.49 feet,more or less to the West line of said Section 17;
> If a GPS will be useful, please let me know if there is any particular
> functionality I will need. Or maybe I could do this just as easy with a
> compass.
> Thanks for your help.
>

'Scratch-Plot' can layout a legal description.

Convert your four-quadrant bearings to azimuths which are clockwise angles
from North. Get UTM North and East coordinates of the found monument. Set up
a scale in 'Scratch-Plot based on the UTM coordinates and largest dimension
of the tract. Enter the UTM coordinates for a point layout, select Azi mode,
and enter the direction and distance calls as lines around the tract...back
to the starting point for a graphical closure.

Finally, navigate to the 'Scratch-Plot' application folder, open the
'Scratch-Plot' file with a text editor, and find the resulting UTM North and
East coordinates within concatenated strings.

Of course the result is approximate because the regional survey is not on
the same directional orientation as either latitude / longitude or UTM...and
only a field survey using any two points could determine the actual
difference in directional orientation...(However, if we assume that the
Federal land subdivision is on the same directional orientation as modern
latitude / longitude then each forward description direction must be rotated
by the amount of convergence found at each starting point...where the
convergence can be found as the difference between latitude / longitude
directions and UTM grid directions between the starting point N,E and a
hypothetical point N + 1852, E .)

KBH

Guest

Posts: n/a

11-26-2005, 10:46 PM

> 'Scratch-Plot' can layout a legal description.
>
> Convert your four-quadrant bearings to azimuths which are clockwise angles
> from North. Get UTM North and East coordinates of the found monument. Set
> up a scale in 'Scratch-Plot' based on the UTM coordinates and largest
> dimension of the tract. Enter the UTM coordinates for a point layout,
> select Azi mode, and enter the direction and distance calls as lines
> around the tract...back to the starting point for a graphical closure.
>
> Finally, navigate to the 'Scratch-Plot' application folder, open the
> 'Scratch-Plot' file with a text editor, and find the resulting UTM North
> and East coordinates within concatenated strings.
>
> Here is a user link to 'Scratch-Plot':
>
> http://www.kbhscape.com/plot.htm
>
>
> Of course the result is approximate because the regional survey is not on
> the same directional orientation as either latitude / longitude or
> UTM...and only a field survey using any two points could determine the
> actual difference in directional orientation...(However, if we assume that
> the Federal land subdivision is on the same directional orientation as
> modern latitude / longitude then each forward description direction must
> be rotated by the amount of convergence found at each starting
> point...where the convergence can be found as the difference between
> latitude / longitude directions and UTM grid directions between the
> starting point N,E and a hypothetical point N + 1852, E .)

(In other words the forward legal description directions would be rotated to
UTM directions using UTM convergence found at each starting point of the
forward direction.)

KBH

Guest

Posts: n/a

11-27-2005, 06:07 PM

Oh, the tract description should also be converted from feet to meters if
working with UTM...

KBH

Guest

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11-28-2005, 08:47 AM

This was the optional or additional section:
> Of course the result is approximate because the regional survey is not on
> the same directional orientation as either latitude / longitude or
> UTM...and only a field survey using any two points could determine the
> actual difference in directional orientation...(However, if we assume that
> the Federal land subdivision is on the same directional orientation as
> modern latitude / longitude then each forward description direction must
> be rotated by the amount of convergence found at each starting
> point...where the convergence can be found as the difference between
> latitude / longitude directions and UTM grid directions between the
> starting point N,E and a hypothetical point N + 1852, E .)

However, I described a method used for an intersection of two directions
while this is a boundary loop...So here there would be one rotation value
and that same rotation value would be applied to all lines. And that's to
rotate the tract description directions (that are based on Federal land
subdivision) into a UTM directional orientation based on a UTM convergence
somewhere on the tract...

Travel by GPS

Guest

Posts: n/a

11-28-2005, 03:41 PM

(E-Mail Removed) wrote:
> Is there a way I
> can convert the legal decription data into a form that is usable in a
> GPS to enable me to at least come close to the marker locations.

I hope this helps!
- Dougwww.TravelByGPS.com
Travel by GPS (tm) Maps Waypoints and Tracks to Adventure

dold@XReXXConve.usenet.us.com

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11-28-2005, 04:27 PM

(E-Mail Removed) wrote:
> I have a nearly square 20 acre property in North Idaho which has been
> surveyed. I know the physical location of one of the metal survey
> markers. I want to locate the other 3 corner markers. Is there a way I
> can convert the legal decription data into a form that is usable in a
> GPS to enable me to at least come close to the marker locations.

"I know the physical location ...".
That's something that bothers me about my plot description.
I don't see anything absolute. I guess that everything is built as a
reference from some point that is not on the page that I have. I don't see
any acknowledgement of any physical starting point.

Consumer GPS is fine for locating the existing corner markers left by some
surveyor, but certainly isn't accurate enough for putting those markers
there.

An error radius of 20 feet or more allows detection of the tall wooden
poles used on my property as survey markers for four out of five marks. I
never did find the one corner that is obscured in heavy brush and trees. I
think I circled around it, but I couldn't find it.

I also couldn't locate my exact ingress point on the cliff for egress. I
missed it, and looking at the track later, I might have been close, but I
can't trust the track within 20 feet either.